Harris DX 25U, Technical Manual

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LOCATION COMPONENT FUNCTION/DESCRIPTION
A7 F2 Pr22 V supply from +15 Volt regulator faults.
B7 F3 Protects -22 V supply from -15 Volt regulator faults.
D5 R15 Audio Gain Adjust. Adjusts audio input sensitivity (audio input level required for 100%
modulation).
E5 R27 Sets maximum output power that can be obtained with the “RAISE” pushbutton.
A2 R41 Dither Frequency Adjust. Adjusts Dither Oscillator frequency (nominally 72 kHz)
B3 R43 Dither Level Adjust. Sets Dither Level; adjusted for minimum noise without excessive
72 kHz sidebands.
B1 R84 Offset. One of four “Modulated B- Supply” adjustments. Refer to the “Tuning/Fre-
quency change” procedure in Section 5, Maintenance.
A1 R85 Gain. Same as “Offset, R84" above.
Table J-3. Analog Input Board A35,
Controls and Indicators
LOCATION COMPONENT FUNCTION/DESCRIPTION
C3 TP1 Audio sample, output of “input amplifier.” (about 1.5 Vp-p audio at 100% modulation,
no DC component).
C3 TP2 Ground
D4 TP3 “Max Pwr Adj” voltage sample (negative DC voltage).
D3 TP4 Inverted (Audio + dc) sample (about 1.5 Vp-p audio at 100% modulation, with -0.75
Volt DC component).
D3 TP5 “Power Supply Sample” (approxi5 VDC).
D3 TP6 Ground.
D2 TP7
“Carrier Power.” Digitally Controlled Potentiometer output (about 2 Vp-p audio with
+1.0 VDC component at 25 kW, 100% mod.
B2 TP8 Ground.
B2 TP9 “Dither” signal (72 kHz triangle wave, typical amplitude less than 5 mV p-p).
B2 TP10 “Dither” oscillator output (72 kHz, 1 Vp-p triangle wave).
C1 TP11 “Big Step Sync” signal.
B4 TP12 Regulated -15 VDC sample.
B7 TP13 Reg5 VDC sample.
C5 TP14 Reg15 VDC sample.
Table J-4. Analog Input Board A35, Test Points
DX-25U
J-6 888-2297-002
WARNING: Disconnect primary power prior to servicing.